In the Copper Plating Solution lab, you placed copper (Cu) pennies in vinegar. Vinegar is a weak acid with hydrogen ions (H+). When you put the pennies in the vinegar, you should have observed small gas bubbles. What were these bubbles composed of, and how did they form?
The bubbles from coming from the copper pennies are hydrogen gas. Free hydrogen ions are plenty in an acid like vinegar unlike water with only to per atom. During the chemical reaction, free hydrogen ions join together to form hydrogen gas.